Database Administrator Authentication

As a DBA, you often perform special operations such as shutting down or starting up a database. Because only a DBA should perform these operations, the database administrator usernames require a secure authentication scheme.

Administrative Privileges

Administrative privileges that are required for an administrator to perform basic database operations are granted through two special system privileges, SYSDBA and SYSOPER. You must have one of these privileges granted to you, depending upon the level of authorization you require.

Note:

The SYSDBA and SYSOPER system privileges allow access to a database instance even when the database is not open. Control of these privileges is totally outside of the database itself.

The SYSDBA and SYSOPER privileges can also be thought of as types of connections that enable you to perform certain database operations for which privileges cannot be granted in any other fashion. For example, if you have the SYSDBA privilege, you can connect to the database by specifying CONNECT AS SYSDBA.

SYSDBA and SYSOPER

The following operations are authorized by the SYSDBA and SYSOPER system privileges:

System Privilege

Operations Authorized

SYSDBA

Perform STARTUP and SHUTDOWN operations

ALTER DATABASE: open, mount, back up, or change character set

CREATE DATABASE

DROP DATABASE

CREATE SPFILE

ALTER DATABASE ARCHIVELOG

ALTER DATABASE RECOVER

Includes the RESTRICTED SESSION privilege

Effectively, this system privilege allows a user to connect as user SYS.

SYSOPER

Perform STARTUP and SHUTDOWN operations

CREATE SPFILE

ALTER DATABASE OPEN/MOUNT/BACKUP

ALTER DATABASE ARCHIVELOG

ALTER DATABASE RECOVER (Complete recovery only. Any form of incomplete recovery, such as UNTIL TIME|CHANGE|CANCEL|CONTROLFILE requires connecting as SYSDBA.)

Includes the RESTRICTED SESSION privilege

This privilege allows a user to perform basic operational tasks, but without the ability to look at user data.

The manner in which you are authorized to use these privileges depends upon the method of authentication that you use.

When you connect with SYSDBA or SYSOPER privileges, you connect with a default schema, not with the schema that is generally associated with your username. For SYSDBA this schema is SYS; for SYSOPER the schema is PUBLIC.

Connecting with Administrative Privileges: Example

This example illustrates that a user is assigned another schema (SYS) when connecting with the SYSDBA system privilege. Assume that the sample user oe has been granted the SYSDBA system privilege and has issued the following statements:

CONNECT oe
CREATE TABLE admin_test(name VARCHAR2(20));

Later, user oe issues these statements:

CONNECT oe AS SYSDBA
SELECT * FROM admin_test;

User oe now receives the following error:

ORA-00942: table or view does not exist

Having connected as SYSDBA, user oe now references the SYS schema, but the table was created in the oe schema.

Selecting an Authentication Method for Database Administrators

Database Administrators can authenticate database administrators through the data dictionary, (using an account password) like other users. Keep in mind that beginning with Oracle Database 11g Release 1, database passwords are case-sensitive. (You can disable case sensitivity and return to pre–Release 11g behavior by setting the SEC_CASE_SENSITIVE_LOGON initialization parameter to FALSE.)

In addition to normal data dictionary authentication, the following methods are available for authenticating database administrators with the SYSDBA or SYSOPER privilege:

Operating system (OS) authentication

Password files

Strong authentication with a network-based authentication service, such as Oracle Internet Directory

These methods are required to authenticate a database administrator when the database is not started or otherwise unavailable. (They can also be used when the database is available.)

The remainder of this section focuses on operating system authentication and password file authentication. See Oracle Database Security Guide for information about authenticating database administrators with network-based authentication services.

Notes:

These methods replace the CONNECT INTERNAL syntax provided with earlier versions of Oracle Database. CONNECT INTERNAL is no longer supported.

Operating system authentication takes precedence over password file authentication. If you meet the requirements for operating system authentication, then even if you use a password file, you will be authenticated by operating system authentication.

Your choice will be influenced by whether you intend to administer your database locally on the same machine where the database resides, or whether you intend to administer many different databases from a single remote client. Figure 1-2 illustrates the choices you have for database administrator authentication schemes.

If you are performing remote database administration, consult your Oracle Net documentation to determine whether you are using a secure connection. Most popular connection protocols, such as TCP/IP and DECnet, are not secure.

Nonsecure Remote Connections

To connect to Oracle Database as a privileged user over a nonsecure connection, you must be authenticated by a password file. When using password file authentication, the database uses a password file to keep track of database user names that have been granted the SYSDBA or SYSOPER system privilege. This form of authentication is discussed in "Using Password File Authentication".

Local Connections and Secure Remote Connections

You can connect to Oracle Database as a privileged user over a local connection or a secure remote connection in two ways:

If the database has a password file and you have been granted the SYSDBA or SYSOPER system privilege, then you can connect and be authenticated by a password file.

If the server is not using a password file, or if you have not been granted SYSDBA or SYSOPER privileges and are therefore not in the password file, you can use operating system authentication. On most operating systems, authentication for database administrators involves placing the operating system username of the database administrator in a special group, generically referred to as OSDBA. Users in that group are granted SYSDBA privileges. A similar group, OSOPER, is used to grant SYSOPER privileges to users.

Using Operating System Authentication

This section describes how to authenticate an administrator using the operating system.

OSDBA and OSOPER

Membership in one of two special operating system groups enables a DBA to authenticate to the database through the operating system rather than with a database user name and password. This is known as operating system authentication. These operating system groups are generically referred to as OSDBA and OSOPER. The groups are created and assigned specific names as part of the database installation process. The default names vary depending upon your operating system, and are listed in the following table:

Operating System Group

UNIX User Group

Windows User Group

OSDBA

dba

ORA_DBA

OSOPER

oper

ORA_OPER

Oracle Universal Installer uses these default names, but you can override them. One reason to override them is if you have more than one instance running on the same host computer. If each instance is to have a different person as the principal DBA, you can improve the security of each instance by creating a different OSDBA group for each instance. For example, for two instances on the same host, the OSDBA group for the first instance could be named dba1, and OSDBA for the second instance could be named dba2. The first DBA would be a member of dba1 only, and the second DBA would be a member of dba2 only. Thus, when using operating system authentication, each DBA would be able to connect only to his assigned instance.

Membership in the OSDBA or OSOPER group affects your connection to the database in the following ways:

If you are a member of the OSDBA group and you specify AS SYSDBA when you connect to the database, then you connect to the database with the SYSDBA system privilege.

If you are a member of the OSOPER group and you specify AS SYSOPER when you connect to the database, then you connect to the database with the SYSOPER system privilege.

If you are not a member of either of these operating system groups and you attempt to connect as SYSDBA or SYSOPER, the CONNECT command fails.

See Also:

Your operating system specific Oracle documentation for information about creating the OSDBA and OSOPER groups

Preparing to Use Operating System Authentication

To enable operating system authentication of an administrative user:

Create an operating system account for the user.

Add the account to the OSDBA or OSOPER operating system defined groups.

Connecting Using Operating System Authentication

A user can be authenticated, enabled as an administrative user, and connected to a local database by typing one of the following SQL*Plus commands:

CONNECT / AS SYSDBA
CONNECT / AS SYSOPER

For the Windows platform only, remote operating system authentication over a secure connection is supported. You must specify the net service name for the remote database:

Connecting Using Password File Authentication

Administrative users can be connected and authenticated to a local or remote database by using the SQL*Plus CONNECT command. They must connect using their username and password and the AS SYSDBA or AS SYSOPER clause. Note that beginning with Oracle Database 11g Release 1, passwords are case-sensitive unless the password file was created with the IGNORECASE=Y option.

For example, user oe has been granted the SYSDBA privilege, so oe can connect as follows:

CONNECT oe AS SYSDBA

However, user oe has not been granted the SYSOPER privilege, so the following command will fail:

CONNECT oe AS SYSOPER

Note:

Operating system authentication takes precedence over password file authentication. Specifically, if you are a member of the OSDBA or OSOPER group for the operating system, and you connect as SYSDBA or SYSOPER, you will be connected with associated administrative privileges regardless of the username/password that you specify.

If you are not in the OSDBA or OSOPER groups, and you are not in the password file, then attempting to connect as SYSDBA or as SYSOPER fails.